The invention relates to a process for generating electric power in an implement inserted into the work spindle of a machine tool, as well as an implement for executing the process.
Implements which consume electric power and which are inserted into the work spindle of a machine tool are known. They can be for example measuring heads. Often, probes are used which require electric power to supply the measuring means or for wireless data transmission. Other devices, such as means for remote measurement by means of ultrasound or optical devices, for example, video cameras, can be used in an implement of this type. Another group of electrical consumers are electric drives located in the implement. They can be, for example, the electric drive of a transverse saddle for boring tools or the spindle drive of an angular drilling machine which is inserted as an implement into the work spindle of a machine tool.
Such implements are inserted instead of a conventional tool into the work spindle of a machine tool. Work is often performed during a preprogrammed and largely automatic production process. Also the implement is often inserted into the work spindle by an automatic tool changer. This precludes an electrical connection of the implement since no electrical connections can be established by the tool changer. An electrical line would have to be plugged into the work spindle by hand after inserting the implement; this would hinder automatic operation. However the implement still requires electric power, whether for taking a measurement, for data communications or for another purpose. Since connection of electrical lines to an implement is complicated for the aforementioned reason, measurement data or other information are also preferably transmitted wirelessly to the machine control. The transmitters and receivers necessary for this purpose consume electric power; high power infrared light transmitters have particularly high power consumption.
One main problem is therefore supply of electric power to the implement. The possibility of using an inductive transformer is already known. In this case a coil located in the implement is inductively coupled to a second coil located in the work spindle of the machine tool. However only smaller power values can be transmitted this way, due to poor magnetic coupling. Another disadvantage of this embodiment is the necessary modification of the work spindle.
Another popular possibility is to use a battery built into the implement. Generally a chargeable battery is used. But this solution is not satisfactory either: batteries lead to frequent maintenance on the implement since they must be changed from time to time. This also applies to batteries which have only a limited service life. Moreover they must be periodically recharged; this requires additional expense. If the implement is not being used, it must be connected to a charging station. Therefore it cannot be placed just anywhere in a tool changer. An implement in the form of a measuring head with built-in battery is known for example from EP-337 671.
Therefore one problem of the invention is to avoid the disadvantages of what is known and to devise a largely maintenance-free electric power source for an implement of the aforementioned type which is insensitive to dirt and enables at low cost comparatively high electric power to be made available. This problem is solved by the invention described below.